Duplex system of telephony



April 18, 1933. H. PAESLER DUPLEX SYSTEM OF TELEPHONY Filed Feb. 8,1927- I Irin- 141144 INVENTOR HANS P s ATTORNEY Patented Apr. 193i HANSPAESLER, 0]! BERLIN, GERMANY, ASSIGNOR T0 F53 DRAHTLOSE TELEGRAPHIE M.B.H.,

, GERMANY Application filed Iebruary 8, 1927, Serial No.

I filed an application Number 31,515 in Germany, February 26, 1926.

High frequency telephony over power lines of' electrical generatingstations involves in the majority of cases telephonic communicationbetween several stations over existing high potential air lines. For'economical reasons the arrangements are so made that in any kind ofsignalling between the two stations which are included in the networkthe same waves are used. This problem of duplex communication is, ingeneral, solved by using difl'erent waves, that is,

oscillations of different frequency for the transmitter and thereceiver. In general, the outgoing or sending wave of one station duringsignalling is the receiving wave of the station communicated with, andvice versa. If it is necessary for any two high frequency stations froma large number of stations connected to the high potential network, tocommunicate with each other, it is necessary that each station besupplied with means for permitting different wave lengths to be used insuch communication. By this it is meant that means must be provided ateach station whereby the exchange or interchange o transmitted andreceived waves may be made. When signalling between stations it isnecessary that the sending and receiving waves of a station should beopposite to what they are at the station to which the signals are sent.1

The transmission oscillation circuits carry radio frequency currents ofconsiderable amplitude, so that a change in its wave would be attendedwith the necessity, relays, and these would have to be built to I meetrequirements as regards sparking and arcing. Ordinary means to suppresssparking are useless in the case of radio frequency circuits. Even ifthe portions of the oscillation circuit to be connected are disposed ina suitable manner with the end in view of minimizing the potentialsarisin across the relay contacts, the ordinary fee le-current relayswill not be usable.

, In accordance with the present invention the change-over to anotherwave is accomplished'while the oscillation circuits of'the f or L0 Cthis circuit depends normally, of

TELErUnxEN ensnusoiau'r or BERLIN, GERMANY, AcoRPoRATI'oN or DUPLEXSYSTEM OF TELEPHONY 166,671; and' in Germany February 26, 1926.

transmitter carry no current, and for this purpose, in some cases thereis required a comparatively simple dependence of the wave relay upon thecallingdevice.

Circuit arrangements as described above are suited for use fortransmission systems in which the change of wave length occurs at thecalling station, and also for systems wherein the change of wave lengthis accomplished at the station called.

This invention will be more fully understood in connection with thedescription of the drawing, wherein:

Figure 1 shows diagrammatically a preferred embodiment of my invention;

Figure 2 illustrates diagrammatically another embodiment thereof inwhich a relay interrupter and a steppingvmechanism device are utilized;while,

Figure 3 diagrammatically illustrates m invention as utilized in acircuit in whic the transmitter exciter runs constantly.

In the arrangement shown in Figures 1 and '2 of the drawing, thefrequency to be generated by the oscillation circuit depends uponwhether the oscillation circuit includes C Whether or not C upon theposition of the switch 71 in each case because winding U can only beenergized to The position of the switch 71 depends upon whether or notsignals from another station are coming in to energize the actuatingwinding J to move '5 into the closed position. .In Figures 1 and 2 thenthe frequency generated can be determined from the callmg station.

Referring to Figure 1, the motor M, utilized for driving the transmitterE, which is here represented as a high frequency alternator, is startedby closing switches g g Closing the switches g 9 connects the motor M tosource 10 and starts the motor rotating. First assume no signal is beingreceived in J. J is deenergized, i is open, and U cannot be energized byway of 9 i, 11, nor by way of h, 11. The frequency of the oscillationsgenerated by E is determined by signal s being received at this stationand t is included in close u when i is closed.

J is energized to close both contacts 71. The switches and switches gare cl'osedand this places'the magnet winding H in series with thesource of energy 10, which energizes the winding H. This closes theswitch contact 72. Since the switches g 9 are closed magnet winding U isenergized through the circuit 9 'i, U, battery 11 etc. Energizingwinding U closes contact u and adds capacity C to the transmitteroscillation circuit LC As will be seen, the frequency of the transmitteroscillation circuit will be changed since the tune of said circuit hasbeen changed by adding C thereto, as described above. The holding magnetH is, as indicated above, en-

ergized and closes a holding circuit h, 11, U

through the magnetic winding U to maintain switch contact'u in theclosed position.

It is necessary that the transmitter circuit be closed at u before thegenerator pro duces oscillations since, as indicated above,

the object of this invention is to prevent changes being made in theoscillation generator circuit during operation. No additional means needbe provided'here to retard Wave generation by E since the change-overrelay U will be operated before the motor M has attained suflicientspeed to run the generator at a speed at which oscillations ofappreciable potential are produced in LG. Upon disconnection of theequipment by opening switches g 9 the holding relay H remains connectedin parallel with the terminals of the motor M. This relay H in practicewill be constructed so as to be very sensitive, and

will remain energized during the entire coasting time of the motor M andgenerator E,

' that is, the time during which a potential still exists across theterminals of the motor M driving the transmitter E. When the potentialacross the terminals of the motor M driving the transmitter E has becomevery low, and also when generation of oscillations by E has ceased, thenrelay II will become deenergized and will. permit it to open.

This opens the circuit'thr'oughwinding U.

removing capacity C from the oscillation circuit so that suchoscillation circuit will be tuned by I'iC only to generate the originalWave. The contact 2' renders the'wave change dependent upon thedirection of the calling "since i is directly controlled by winding J.

ever, simultaneously with the closing of the .motor circuit by way of 9the switch 9 When 1 is closed a circuit 9 the arm of V, V, i, battery11, and winding D is completed. The winding D is energized and the armconnected with the plunger of D moves ratchetwheel K forward one step,thereby closing the circuit of the changeover relay U. Leaving itsinitial position the arm connected with K opens the circuit of thedrivin magnet D. T he motor M starts slowly and the relay U. energizedby way of 2', the arm of V, V, U and 11, operates with sufficient speedso that the oscillation circuit L, C C;- is completed, that is, C addedto said circuit, before the transmitter E generates oscillations ofappreciable amplitude.

Vhen it is desired to stop the generator, switches {/2 are opened tostop the driving motor M. A circuit B, U, D is closed, and the drivingmagnet D is energized intermittently by the running chopper orinterrupter B. The interrupter B may be of any known type. 'The armconnected with the plunger of I) is actuated and K is simultaneouslystepped forward during the operation of the circuit interrupter. in thismanner retu rn-' ing said arm to its initial position after a certainnlunber of steps. It is only in this initial position that boththecircuits of the reaches its initial position. Naturally the circmts'canhe so arranged that the excitalion of the changing-over relay can beef-- fectuated after the switches g 9 are in the state of rest,Likewise, it makes no difference whether the. relays-are operated byopen or closed circuit working.

Here the switch it is never operated while oscillations are beingdeveloped in the cir- ('HitLC, Here also the frequency developed may bedetermined by the calling station since the nosition'of u depends onwhether- J is energized or not. w

In Figures 1 and 2 the frequency gener ated is detern'lined by theposition of i. The position of i in turn depends upon whether signalsare. coming in from another station or not. In other words, thefrequency pro dueed by I) and associated circuit is controlled in partat least by another calling station. In the arrangement ofFigure to hedescribed hereinafter, the frequency developed is determined at thesending station, i. e., at E, and is not determined at the callingstation.

In Figure 3 the changing-over of the wave lengths takes place with thedriving motor of the transmitter running. Thepresent invention howeverprovides means whereby the changes in the frequency determining circuitare made before said circuits are appreciably energized by the generatoror after the amplitude of the oscillations produced therein due to,excitation by the generator has fallen to a low value or theoscillations have stopped.

This figure illustrates the case where the high frequency alternator E.driven from motor M, and which serves for exciting a transmitteramplifier 12, runs constantly. This generator E may supply, forinstance, the input circuit of the power amplifier 12 with a radiofrequency potential either directly or by way of transforming means. IfC here a change in wave-length is to be effected while the set ME isrunning, care must be taken to insure that the transmitter is preventedfrom exciting 12' and the circuit L0 before said change is made. Thismay be accomplished by short-circuiting E by closing the switch t In thedrawing, as

shown, the relay U in addition to controlling the switch M for thewave-change, controls also the working contacts M and te The relay Tcontrols the working contacts t and t the relay V operates amake-and-break contact '0 which, in the drawing, is shown to be in itsposition of rest (left-hand position) at which position the relay V ispresumed to be deenergized.

To produce one wave or frequency the two double-throw switches s 8 arechanged over conjointly into their left-hand position. To produce theother wave-length or frequency, they are again conjointly changed overinto the right-hand position. These switches may be coordinated with thetelephone receiver in this manner that. when the same is being liftedoff, they are caused to move into their working position on the lefthandside, and when replacing the receiver. they are moved to their positionof, rest towards the right-hand side.

If the double-throw switches s for initiating wave-change, are moved tothe left. the winding of relay T will be energized by current from 11 bvway of w and 8 The armature of relay T will actuate its switches 25,, tBy the closure of f the transmitter is rendered inoperative, due to theshort circuit completed by way of and the oscillation circuits LC; C inwhich the switching operations are to be performed. will carry nocurrent. tact t energizes the winding of t e relav U by way of theswitch s moved over to the left-hand side, battery 11, resistance WW.the winding of U, and back to i The armature of U closes contacts u Mand m. This wave-change accomplished by u therefore The simultaneousclos ng of con-- takes place only after E has been short circuited by tThe closing of the contact u completes a holding circuit by way of Mbattery 11, and resistance 'Wd through the winding of relay U so thatthis winding remains energized, irrespective of whether the contact t isopened again or not. The closing of con tact u causes energization ofthe winding of relay V byway of circuit a battery 11 and the winding ofV. \Vhen V is energized the contact a) is pulled to the left so that thecircuit for T, which had previously been closed by way of the contact 8,in the left-hand side, is now opened. The result is that after u, isclosed t opens so that wave generation is resumed. The frequency of theoscillations generated is determined by LC, and

Now, if the frequency of the wave generated is to be changed again, i.e., determined by LC then the switches s 8 are moved to the right-hand.position as shown. Since 1;

is now in its right-hand position, owing to the continued energizationof the winding of V the winding of T will be energized by current from11 by way of the two switches w and s, which has been moved to therighthand position. The winding of T being energized will causeinterruption of the wave generation by virtue of the fact that It, willbe closed. Furthermore, 25 will be closed, and the winding of U will beshort-circuited by way of a circuit through t and the switch '8 which isin the right-hand position. The contacts associated with V open. Openingof the contact u restores the oscillation circuit LC to the position asillustrated. That is C is'no longer included in this circuit. Theopening of the contact M2 separates or opens the holding circuit whichstill existed between the end of winding U and the battery 11. Theopening of contact u breaks the circuit through the winding of V. 1 ismoved over into the left-hand position as illustrated interrupting thecircuit through the winding of T. t, is opened again, and the shortcircuit removed from E. The generation of waves by E and the amplifierat a frequency determined by LC, is resumed. The change in the tune ofthe circuit has in all cases been effected in the absence of currentflow in the frequency determining circuit.

I claim as my invention 1. In radio frequency communication systemsincluding an oscillation generator having a frequency determiningcircuit and means for changing the tune of said circuit, switching meansfor putting said oscillation generator into operation, means associatedwith said switching means and with the frequency determining means inthe circuit of said oscillation generator for insuring that the changein the tune of said circuit iscomtude, and means for preventing changein said frequency determlning circuit from being made when saidgenerator is stopped until said generator stops producing oscillationsin said circuit.

2. In radio frequency com'nnmication systems comprising a plurality ofstations, each includ ng an oscillation generator having a frequencydetermining circuit and means for changing the tune of said circuit, anda receiver adapted to receive signals from a similar station, switchingmeans at said station for putting said oscillation generator intooperation, means associated with said receiver and with the frequencydetermining means in the circuit of said oscillation generator forpreventing the tune of said circuit from being changed while saidgenerator remains in operation except when signals are received on saidreceiver, and means at said station for preventing a change in the tuneof said frequency determining circuit from being made when saidswitching means is actuated to put said generator out of operation untilsaid generator has stopped producing oscillations of appreciableamplitude insaid frequency 'determining circuit.

In a high frequency radio communication system comprising a plurality ofstations, each including an oscillation generator,

- a frequency'determining circuit connected with said generator andmeans for changing the tune of said circuit, and a receiver to receive]signals from a similar station, the receiver and transmitter operatingat different frequencies, means at said station for starting saidgenerator whereby said generator normally produces a predeterminedfrequency, means connected with said receiving means and actuated bysignal received there- 7 in for preparing means to change the tune of ofthe frequency determining circuit are made said frequency determiningcircuit and the frequency of the oscillations produced when saidgenerator is started, said last two means including means wherebychanges in the tune before the generator developes oscillations ofappreciable amplitude,and means associated with said circuit preparingmeans and frequency determining circuit changing means for inhibitingchanges in the tune of said frequency determining circuit when saidgenerator is stopped until the oscillations-produced in said circuit areof small amplitude.

4. A high frequency radio communcation system including an oscillationgenerator, a tuned circuit connected with said generator to determinethe frequency of the oscillations generated, an additional tuningelement, switching means for connecting said additional element 1n sa dcircuit to change the tune thereof and the frequency of the oscillationsgenerated, an actuating relay connected tune thereof, and to change thefrequency of the oscillations developed, means for prevent ing thedevelopment by said generator of oscillations of appreciable amplitudebefore the switching action is completed, and means associated with saidrelays for preventing said switch from being opened by thedeenergization of said relay circuit when said generator is stoppeduntil the oscillations produced in said circuit are of small amplitude.

HANS PAESLER.

